Method of microbial enhanced oil recovery

Abstract

A method of microbial enhanced oil recovery for recovering oil from an oil-bearing rock formation ( 13 ). The method comprises: injecting water containing a source of vitamins, phosphates and an electron acceptor such as nitrate into the formation at first location ( 10 ) and allowing anaerobic bacteria, which are either already present in the formation ( 13 ) or which are introduced simultaneously to multiply using the oil as their main carbon source. This establishes a biomass layer ( 16 ) which acts to dissociate the oil from the rock formation ( 13 ). The dissociated oil is removed via an outlet ( 15 ).

What is claimed is:  
     
       1. A method of microbial enhanced oil recovery for recovering oil from an oil-bearing rock formation, the formation including an inlet and at least one outlet, the method comprising: 
       infecting water containing a source of vitamins, phosphates and an electron acceptor into the formation;  
       allowing micro-organisms selected from the group consisting of anaerobic and facultative anaerobic bacteria to multiply using the oil as their main carbon source, thereby establishing a biomass layer which acts to dissociate the oil from the rock formation; and  
       removing the dissociated oil via the at least one outlet;  
       wherein the micro-organisms substantially comprise species selected from the group consisting of sulphate-reducing bacteria, nitrate-reducing bacteria, iron-reducing bacteria, acetogenic bacteria, and combinations of these.  
     
     
       2. A method as claimed in  claim 1 , in which the microorganisms are already present in the formation. 
     
     
       3. A method as claimed in  claim 1 , in which the microorganisms are introduced simultaneously with the vitamins, phosphates and electron acceptor. 
     
     
       4. A method as claimed in  claim 1 , in which the electron acceptor is nitrate. 
     
     
       5. A method as claimed in  claim 1 , in which the inlet is at a first location and the outlet is at a second location spaced apart from the first location. 
     
     
       6. A method as claimed in  claim 1 , in which the inlet and outlet are one and the same. 
     
     
       7. A method as claimed in  claim 1 , in which substantially no oxygen is supplied with the injection water. 
     
     
       8. A method as claimed in  claim 1 , in which the source of vitamins comprises vitamins selected from the group consisting of B12, biotin, folic acid, nicotinic acid, aminobenzoic acid, calcium pantothenate, pyridoxine HCL, riboflavin, thiamine and thioctic acid. 
     
     
       9. A method as claimed in  claim 1 , in which the source of vitamins is introduced into the formation continuously. 
     
     
       10. A method as claimed in  claim 1 , in which the concentration of the source of vitamins in the injection water is in the range of 1 to 1000 μg/l. 
     
     
       11. A method as claimed in  claim 1 , in which the superficial velocity of the injection water through the oil-bearing formation is between 0.1 and 15 m/day. 
     
     
       12. A method as claimed in  claim 1 , in which the microorganisms produce surfactants which act to dislodge the oil. 
     
     
       13. A method as claimed in  claim 1 , applied to more than one outlet from the oil-bearing formation. 
     
     
       14. A method of microbial enhanced oil recovery for recovering oil from an oil bearing rock formation, the method comprising: 
       a step for supplying a substance for promoting microbial growth to the formation;  
       a step for creating a biomass layer in the formation for dissociating oil from the formation; and  
       a step for removing the dissociated oil from the formation, wherein the substance for promoting microbial growth comprises water, a source of vitamins, a source of phosphates, and an electron acceptor; and  
       wherein the source of vitamins comprises at least one vitamin selected from the group consisting of B12, biotin, folic acid, nicotinic acid, aminobenzoic acid, calcium pantothenate, pyridoxine HCL, riboflavin, thiamine, and thioctic acid.  
     
     
       15. The method of  claim 14 , wherein the step for supplying a substance for promoting microbial growth to the formation comprises injecting the substance at an inlet to the formation. 
     
     
       16. The method of  claim 15 , wherein the superficial velocity of the substance through the formation is in the range from 0.1 to 15 m/day. 
     
     
       17. The method of  claim 14 , wherein the electron acceptor comprises nitrate. 
     
     
       18. The method of  claim 14 , wherein the concentration of the source of vitamins in the substance is in the range of 1 to 1000 μg/l. 
     
     
       19. The method of  claim 14 , wherein substantially no oxygen is supplied with the substance for promoting microbial growth. 
     
     
       20. The method of  claim 14 , wherein the step for creating a biomass layer in the formation comprises allowing bacteria selected from the group consisting of anaerobic and facultative anaerobic bacteria to multiply using the oil as their main carbon source. 
     
     
       21. The method of  claim 20 , wherein the bacteria are already present in the formation. 
     
     
       22. The method of  claim 20 , wherein the bacteria are introduced simultaneously with the substance for promoting microbial growth. 
     
     
       23. The method of  claim 20 , wherein the bacteria include at least one species selected from the group consisting of sulphate reducing bacteria, nitrate reducing bacteria, iron reducing bacteria and acetogenic bacteria. 
     
     
       24. A method of microbial enhanced oil recovery for recovering oil from an oil-bearing rock formation, the formation including an inlet and at least one outlet, the method comprising: 
       injecting water containing a source of vitamins, phosphates and an electron acceptor into the formation;  
       allowing micro-organisms selected from the group consisting of anaerobic and facultative anaerobic bacteria to multiply using the oil as their main carbon source, thereby establishing a biomass layer which acts to dissociate the oil from the rock formation; and  
       removing the dissociated oil via the at least one outlet,  
       wherein the source of vitamins comprises vitamins selected from the group consisting of B12, biotin, folic acid, nicotinic acid, aminobenzoic acid, calcium pantothenate, pyridoxine HCL, riboflavin, thiamine and thioctic acid.  
     
     
       25. A method as claimed in  claim 24 , in which substantially no oxygen is supplied with the injection water. 
     
     
       26. A method as claimed in  claim 24 , in which the concentration of the source of vitamins in the injection water is in the range of 1 to 1000 μg/l. 
     
     
       27. A method as claimed in  claim 24 , in which the superficial velocity of the injection water through the oil-bearing formation is between 0.1 and 15 m/day. 
     
     
       28. A method as claimed in  claim 24 , in which the micro-organisms produce surfactants which act to dislodge the oil. 
     
     
       29. The method of  claim 24 , wherein the micro-organisms include at least one species selected from the group consisting of sulphate reducing bacteria, nitrate reducing bacteria, iron reducing bacteria and acetogenic bacteria. 
     
     
       30. A method of microbial enhanced oil recovery for recovering oil from an oil bearing rock formation, the method comprising: 
       a step for supplying a substance for promoting microbial growth to the formation;  
       a step for creating a biomass layer in the formation for dissociating oil from the formation; and  
       a step for removing the dissociated oil from the formation,  
       wherein the substance for promoting microbial growth comprises water, a source of vitamins, a source of phosphates, and an electron acceptor, and wherein the step for creating a biomass layer in the formation comprises allowing bacteria selected from the group consisting of anaerobic and facultative anaerobic bacteria to multiply using the oil as their main carbon source, and wherein the bacteria include at least one species selected from the group consisting of sulphate reducing bacteria, nitrate reducing bacteria, iron reducing bacteria and acetogenic bacteria.  
     
     
       31. A method as claimed in  claim 30 , in which substantially no oxygen is supplied with the injection water. 
     
     
       32. A method as claimed in  claim 30 , in which the concentration of the source of vitamins in the injection water is in the range of 1 to 1000 μg/l. 
     
     
       33. A method as claimed in  claim 30 , in which the superficial velocity of the injection water through the oil-bearing formation is between 0.1 and 15 m/day. 
     
     
       34. A method as claimed in  claim 30 , in which the bacteria produce surfactants which act to dislodge the oil. 
     
     
       35. A method as claimed in  claim 30 , wherein the source of vitamins comprises vitamins selected from the group consisting of B12, biotin, folic acid, nicotinic acid, aminobenzoic acid, calcium pantothenate, pyridoxine HCL, riboflavin, thiamine and thioctic acid. 
     
     
       36. A method of microbial enhanced oil recovery for recovering oil from an oil-bearing rock formation, the formation including an inlet and at least one outlet, the method comprising: 
       injecting water containing a source of vitamins, phosphates and an electron acceptor into the formation;  
       allowing micro-organisms selected from the group consisting of anaerobic and facultative anaerobic bacteria to multiply using the oil as their main carbon source, thereby establishing a biomass layer which acts to dissociate the oil from the rock formation; and  
       removing the dissociated oil via the at least one outlet, wherein substantially no oxygen is supplied with the injection water.  
     
     
       37. A method as claimed in  claim 36 , in which the concentration of the source of vitamins in the injection water is in the range of 1 to 1000 μg/l. 
     
     
       38. A method as claimed in  claim 36 , in which the superficial velocity of the injection water through the oil-bearing formation is between 0.1 and 15 m/day. 
     
     
       39. A method as claimed in  claim 36 , in which the micro-organisms produce surfactants which act to dislodge the oil. 
     
     
       40. A method as claimed in  claim 36 , wherein the source of vitamins comprises vitamins selected from the group consisting of B12, biotin, folic acid, nicotinic acid, aminobenzoic acid, calcium pantothenate, pyridoxine HCL, riboflavin, thiamine and thioctic acid. 
     
     
       41. The method of  claim 36 , wherein the micro-organisms include at least one species selected from the group consisting of sulphate reducing bacteria, nitrate reducing bacteria, iron reducing bacteria and acetogenic bacteria. 
     
     
       42. A method of microbial enhanced oil recovery for recovering oil from an oil bearing rock formation, the method comprising: 
       a step for supplying a substance for promoting microbial growth to the formation;  
       a step for creating a biomass layer in the formation for dissociating oil from the formation; and  
       a step for removing the dissociated oil from the formation, wherein the substance for promoting microbial growth comprises water, a source of vitamins, a source of phosphates, and an electron acceptor, wherein substantially no oxygen is supplied with the substance for promoting microbial growth.  
     
     
       43. A method as claimed in  claim 42 , in which the concentration of the source of vitamins in the injection water is in the range of 1 to 1000 μg/l. 
     
     
       44. A method as claimed in  claim 42 , in which the superficial velocity of the injection water through the oil-bearing formation is between 0.1 and 15 m/day. 
     
     
       45. A method as claimed in  claim 42 , in which the bacteria produce surfactants which act to dislodge the oil. 
     
     
       46. A method as claimed in  claim 42 , wherein the source of vitamins comprises vitamins selected from the group consisting of B12, biotin, folic acid, nicotinic acid, aminobenzoic acid, calcium pantothenate, pyridoxine HCL, riboflavin, thiamine and thioctic acid. 
     
     
       47. The method of  claim 42 , wherein the micro-organisms include at least one species selected from the group consisting of sulphate reducing bacteria, nitrate reducing bacteria, iron reducing bacteria and acetogenic bacteria.